Physics
Induced Potential
Induced potential refers to the creation of an electromotive force in a conductor due to a changing magnetic field. This phenomenon is governed by Faraday's law of electromagnetic induction, which states that a changing magnetic field induces an electric current in a nearby conductor. Induced potential plays a crucial role in the generation of electricity in power plants and the functioning of electric generators and transformers.
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10 Key excerpts on "Induced Potential"
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
This case is called an induced EMF. On the other hand, when the magnet is stationary and the conductor is rotated, the moving charges experience a magnetic force (as described by the Lorentz force law), and this magnetic force pushes the charges through the wire. This case is called motional EMF. Electrical motor An electrical generator can be run backwards to become a motor. For example, with the Faraday disc, suppose a DC current is driven through the conducting radial arm by a voltage. Then by the Lorentz force law, this traveling charge experiences a force in the magnetic field B that will turn the disc in a direction given by Fleming's left hand rule. In the absence of irreversible effects, like friction or Joule heating, the disc turns at the rate necessary to make d Φ B / dt equal to the voltage driving the current. ________________________ WORLD TECHNOLOGIES ________________________ Electrical transformer The EMF predicted by Faraday's law is also responsible for electrical transformers. When the electric current in a loop of wire changes, the changing current creates a changing magnetic field. A second wire in reach of this magnetic field will experience this change in magnetic field as a change in its coupled magnetic flux, a d Φ B / d t . Therefore, an electromotive force is set up in the second loop called the induced EMF or transformer EMF . If the two ends of this loop are connected through an electrical load, current will flow. Magnetic flow meter Faraday's law is used for measuring the flow of electrically conductive liquids and slurries. Such instruments are called magnetic flow meters. The induced voltage ℇ generated in the magnetic field B due to a conductive liquid moving at velocity v is thus given by: , where ℓ is the distance between electrodes in the magnetic flow meter.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- University Publications(Publisher)
This case is called an induced EMF. On the other hand, when the magnet is stationary and the conductor is rotated, the moving charges experience a magnetic force (as described by the Lorentz force law), and this magnetic force pushes the charges through the wire. This case is called motional EMF. Electrical motor An electrical generator can be run backwards to become a motor. For example, with the Faraday disc, suppose a DC current is driven through the conducting radial arm by a voltage. Then by the Lorentz force law, this traveling charge experiences a force in the magnetic field B that will turn the disc in a direction given by Fleming's left hand rule. In the absence of irreversible effects, like friction or Joule heating, the disc turns at the rate necessary to make d Φ B / dt equal to the voltage driving the current. ____________________ WORLD TECHNOLOGIES ____________________ Electrical transformer The EMF predicted by Faraday's law is also responsible for electrical transformers. When the electric current in a loop of wire changes, the changing current creates a changing magnetic field. A second wire in reach of this magnetic field will experience this change in magnetic field as a change in its coupled magnetic flux, a d Φ B / d t . Therefore, an electromotive force is set up in the second loop called the induced EMF or transformer EMF . If the two ends of this loop are connected through an electrical load, current will flow. Magnetic flow meter Faraday's law is used for measuring the flow of electrically conductive liquids and slurries. Such instruments are called magnetic flow meters. The induced voltage ℇ gen-erated in the magnetic field B due to a conductive liquid moving at velocity v is thus given by: , where ℓ is the distance between electrodes in the magnetic flow meter.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Orange Apple(Publisher)
This case is called an induced EMF. On the other hand, when the magnet is stationary and the conductor is rotated, the moving charges experience a magnetic force (as described by the Lorentz force law), and this magnetic force pushes the charges through the wire. This case is called motional EMF. Electrical motor An electrical generator can be run backwards to become a motor. For example, with the Faraday disc, suppose a DC current is driven through the conducting radial arm by a voltage. Then by the Lorentz force law, this traveling charge experiences a force in the magnetic field B that will turn the disc in a direction given by Fleming's left hand rule. In the absence of irreversible effects, like friction or Joule heating, the disc turns at the rate necessary to make d Φ B / dt equal to the voltage driving the current. Electrical transformer The EMF predicted by Faraday's law is also responsible for electrical transformers. When the electric current in a loop of wire changes, the changing current creates a changing ________________________ WORLD TECHNOLOGIES ________________________ magnetic field. A second wire in reach of this magnetic field will experience this change in magnetic field as a change in its coupled magnetic flux, a d Φ B / d t . Therefore, an electromotive force is set up in the second loop called the induced EMF or transformer EMF . If the two ends of this loop are connected through an electrical load, current will flow. Magnetic flow meter Faraday's law is used for measuring the flow of electrically conductive liquids and slurries. Such instruments are called magnetic flow meters. The induced voltage ℇ generated in the magnetic field B due to a conductive liquid moving at velocity v is thus given by: , where ℓ is the distance between electrodes in the magnetic flow meter.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
This case is called an induced EMF. On the other hand, when the magnet is stationary and the conductor is rotated, the moving charges experience a magnetic force (as described by the Lorentz force law), and this magnetic force pushes the charges through the wire. This case is called motional EMF. Electrical motor An electrical generator can be run backwards to become a motor. For example, with the Faraday disc, suppose a DC current is driven through the conducting radial arm by a voltage. Then by the Lorentz force law, this traveling charge experiences a force in the magnetic field B that will turn the disc in a direction given by Fleming's left hand rule. In the absence of irreversible effects, like friction or Joule heating, the disc turns at the rate necessary to make d Φ B / dt equal to the voltage driving the current. ________________________ WORLD TECHNOLOGIES ________________________ Electrical transformer The EMF predicted by Faraday's law is also responsible for electrical transformers. When the electric current in a loop of wire changes, the changing current creates a changing magnetic field. A second wire in reach of this magnetic field will experience this change in magnetic field as a change in its coupled magnetic flux, a d Φ B / d t . Therefore, an electromotive force is set up in the second loop called the induced EMF or transformer EMF . If the two ends of this loop are connected through an electrical load, current will flow. Magnetic flow meter The third most common flowmeter behind differential pressure and positive displacement flow meters, is the magnetic flow meter , also technically an electromagnetic flow meter or more commonly just called a mag meter . A magnetic field is applied to the metering tube, which results in a potential difference proportional to the flow velocity per-pendicular to the flux lines. The physical principle at work is electromagnetic induction.
eBook - PDFElectrotechnics N4 Student's Book
TVET FIRST
- SA Chuturgoon(Author)
- 2021(Publication Date)
- Troupant(Publisher)
● What is the difference between a dynamically induced emf and a statically induced emf? 3 Principles of electricity TVET FIRST Potential difference is represented by the symbol V or PD and is measured in joules per coulomb or volts (V). Definition of coulomb The coulomb is the SI unit of electrical charge equal to the quantity of electricity conveyed in 1 s by a current of 1 A. Definition of volt The volt is the potential difference between two points of a conducting wire carrying a constant current of 1 A when the power dissipated between these points is equal to 1 W. 1.1.3 Electromotive force (emf) Electromotive force is an electrical potential produced by any source of electrical energy. Its function is to initiate and maintain a potential difference. Electromotive force, often referred to as emf, is represented by the symbol E and is also measured in volts (V). Definition of electromotive force (emf) Electromotive force is the voltage measured across the ends of a voltage source of an open circuit , that is, when no current is flowing. Sources of electromotive force The following are the sources of electromotive force or sources of electrical energy: • Cells or batteries. • Generators . • Solar energy . • Heat. • Friction . Electromotive force versus potential difference Did you notice that potential difference and electromotive force are both measured in volts? It has become common practice over the years to refer to potential difference and electromotive force as voltage (which also means electrical potential). So, let us highlight the differences between the two in order to avoid confusion. Electromotive force (emf) is the voltage (electrical potential) measured across the terminals of an electrical energy source of an open circuit, that is, when no current is flowing through the circuit.
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
550 Chapter 22 | Electromagnetic Induction 22.1 | Induced Emf and Induced Current There are a number of ways a magnetic field can be used to generate an electric current, and Figure 22.1 illustrates one of them. This drawing shows a bar magnet and a helical coil of wire to which an ammeter is connected. When there is no relative motion between the magnet and the coil, as in part a of the drawing, the ammeter reads zero, indicating that no current exists. However, when the magnet moves toward the coil, as in part b, a current I appears. As the magnet approaches, the magnetic field B B that it creates at the location of the coil becomes stronger and stronger, and it is this changing field that produces the current. When the magnet moves away from the coil, as in part c, a current is also pro- duced, but with a reversed direction. Now the magnetic field at the coil becomes weaker as the magnet moves away. Once again it is the changing field that generates the current. A current would also be created in Figure 22.1 if the magnet were held stationary and the coil were moved, because the magnetic field at the coil would be changing as the coil approached or receded from the magnet. Only relative motion between the magnet and the coil is needed to generate a current; it does not matter which one moves. The current in the coil is called an induced current because it is brought about (or “in- duced”) by a changing magnetic field. Since a source of emf (electromotive force) is always needed to produce a current, the coil itself behaves as if it were a source of emf. This emf is known as an induced emf. Thus, a changing magnetic field induces an emf in the coil, and the emf leads to an induced current. 22 | Electromagnetic Induction © Jeff Greenberg/Age Fotostock Electric guitars are famous for their amplified and manipulatable sound. To produce this sound, virtually all of them have one or more electro- magnetic pickups located beneath the strings (see Section 22.6).
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
22.2 Motional Emf 627 In each of the previous examples, both an emf and a current are induced in the coil because the coil is part of a complete, or closed, circuit. If the circuit were open—perhaps because of an open switch—there would be no induced current. However, an emf would still be induced in the coil, whether the current exists or not. Changing a magnetic field and changing the area of a coil are methods that can be used to create an induced emf. The phenomenon of producing an induced emf with the aid of a magnetic field is called electromagnetic induction. The next section discusses yet another method by which an induced emf can be created. Check Your Understanding (The answer is given at the end of the book.) 1. Suppose that the coil and the magnet in Interactive Figure 22.1a were each moving with the same velocity relative to the earth. Would there be an induced current in the coil? 22.2 Motional Emf The Emf Induced in a Moving Conductor When a conducting rod moves through a constant magnetic field, an emf is induced in the rod. This special case of electromagnetic induction arises as a result of the magnetic force that acts on a moving charge (see Section 21.2). Consider the metal rod of length L moving to the right in Animated Figure 22.4a. The velocity v → of the rod is constant and is perpendicular to a uniform magnetic field B → . Each charge q within the rod also moves with a velocity v → and experiences a magnetic force of magnitude F = ∣ q∣ B, according to Equation 21.1. By using RHR-1, it can be seen that the mobile, free electrons are driven to the bottom of the rod, leaving behind an equal amount of positive charge at the top. (Remember to reverse the direction of the force that RHR-1 predicts, since the electrons have a negative charge. See Section 21.2.) The positive and negative charges accumulate until the attractive electric force that they exert on each other becomes equal in magnitude to the magnetic force.
eBook - PDFElectromagnetism for Engineers
An Introductory Course
- P. Hammond(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
describes a conservative field and is associated with magnetic potentials and H2 describes a non-conservative field and is associated with magnetomotive force. We now have a parallel situation in electricity. The electrostatic field strength E^ is due to electric charges and is associated with a conservative field and potential, while Electromagnetic Induction 109 ^ = E. electrostatic (6.17) In Section 4.4 we pointed out that an electromotive force is necessary to circulate electric current and that most generators rely for their electromotive force on the motion of conductors through magnetic fields. Let us consider this process in detail. Figure 6.7 shows a conductor of length / moving with £2 ''vB F IG. 6.7 Motional electric field strength in a conductor velocity υ across a uniform magnetic field B. The charges in the conductor will experience an electric field strength ν Β and the free electrons will move as far as they can, i.e. a surface charge will appear on the conductor (Fig. 6.8). When the electrons cease to move, the amount of the surface charge will be such as to provide an electrostatic field strength which is equal and opposite to vB. The F IG. 6.8 Electrostatic field cancels motional field the motional electric field strength of eqn. (6.16) is associated with a non-conservative field and electromotive force. Just as the total magnetic field strength is the sum of and so is the total electric field strength experienced by a charge the sum of the two components and £2· 110 Electromagnetism for Engineers V = -E , d/ ^E^ál = vBl (6.18) The electromotive force will be e.m.f. = E2 dl = vBl (6.19) Thus the e.m.f. and the p.d. are equal. So far the moving conductor does not supply current, because there is no circuit, but now consider the arrangement of Fig. 6.9 where there is a closed circuit. A thick conductor slides with velocity ν between two thick conducting bars through a magnetic field B.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter 9 Faraday's Law of Induction Faraday's law of induction is a basic law of electromagnetism relating to the operating principles of transformers, inductors, and many types of electrical motors and generators. The law states that: The induced electromotive force (EMF) in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit. Or alternatively: The EMF generated is proportional to the rate of change of the magnetic flux. History Electromagnetic induction was discovered independently by Michael Faraday and Joseph Henry in 1831; however, Faraday was the first to publish the results of his experiments. ____________________ WORLD TECHNOLOGIES ____________________ Faraday's disk In Faraday's first experimental demonstration of electromagnetic induction (August 1831), he wrapped two wires around opposite sides of an iron torus (an arrangement similar to a modern transformer). Based on his assessment of recently-discovered properties of electromagnets, he expected that when current started to flow in one wire, a sort of wave would travel through the ring and cause some electrical effect on the opposite side. He plugged one wire into a galvanometer, and watched it as he connected the other wire to a battery. Indeed, he saw a transient current (which he called a wave of electricity) when he connected the wire to the battery, and another when he disconnected it. Within two months, Faraday had found several other manifestations of electromagnetic induction. For example, he saw transient currents when he quickly slid a bar magnet in and out of a coil of wires, and he generated a steady (DC) current by rotating a copper disk near a bar magnet with a sliding electrical lead (Faraday's disk). Faraday explained electromagnetic induction using a concept he called lines of force.
eBook - PDFElectric Safety
Practice and Standards
- Mohamed A. El-Sharkawi(Author)
- 2013(Publication Date)
- CRC Press(Publisher)
voltage. induced. on. it. through. electric. field. (capacitive. coupling). induc-tion. .This.voltage.will.have.a.magnitude.somewhere.between.zero.voltage. (ground).and.the.voltage.of.the.energized.line . .In.practical.circumstances,. induced.voltage.can.be.as.high.as.30%.of.the.energized.line.voltage . Magnetic. fields. can. induce. hazardous. open. circuit. voltages. in. par-tially.grounded.loops.of.de-energized.lines.adjacent.to.energized.lines . . This.voltage.can.be.as.high.as.300.V/mile.under.normal.load.conditions. or. as. high. as. 5000. V/mile. under. short. circuit. conditions . . In. addition,. hazardous.current.levels.can.be.induced.in.grounded.loops.to.levels.that. create.hazardous.step.or.touch.voltages.at.or.near.ground.electrodes . 126 Electric Safety In.this.chapter,.we.shall.study.induced.voltage.due.to.the.electric.field. alone. . Induced. voltage. due. to. magnetic. field. is. covered. in. the. next. Chapter.7 . 6.1 Equipotential Surface To.understand.the.effect.of.electric.field,.we.start.with.the.simple.case.shown. in.Figure.6 .2. .This.is.for.a.charged.sphere.located.high.enough.above.ground . . This.way,.the.electric.field.is.uniformly.distributed.and.is.free.from.ground. distortions. .The.charge. Q .produces.an.electric.field.in.the.radial.direction. from.the.surface.of.the.sphere . .Any.two.points.outside.the.sphere.that.are. located.at.the.same.distance.from.the.center.of.the.sphere.will.have.identical. potential. .Thus,.any.imaginary.sphere.in.the.air.that.is.concentric.with.the. charged.sphere.will.have.no.voltage.difference.between.any.two.points.on. its.surface . .This.is.known.as.the. equipotential surface . The. electric. field. is. dense. at. the. surface. of. the. sphere. and. becomes. less. dense.when.we.move.away . .The.electric.field.density. D x .at.an.equipotential. surface.whose.radius. x .can.be.expressed.by . D Q A Q x x x = = 4 2 π .
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